[Python-ideas] Allow mutable builtin types (optionally)

Eloi Gaudry Eloi.Gaudry at fft.be
Thu Jun 21 11:26:37 EDT 2018

This request didn't have a lot of traction, but I still consider this is something that would need to be supported (2 lines of code to be changed; no regression so far with python 2 and python 3).

My main points are:

- HEAP_TYPE is not really used (as anyone being using it ?)

- HEAP_TYPE serves other purposes

- extension would benefit for allowing direct access to any of its type attributes

Petr, what do you think ?


From: Python-ideas <python-ideas-bounces+eloi.gaudry=fft.be at python.org> on behalf of Eloi Gaudry <Eloi.Gaudry at fft.be>
Sent: Tuesday, May 8, 2018 9:26:47 AM
To: encukou at gmail.com; python-ideas at python.org
Subject: Re: [Python-ideas] Allow mutable builtin types (optionally)

On Mon, 2018-05-07 at 15:23 -0400, Petr Viktorin wrote:
> On 05/07/18 11:37, Eloi Gaudry wrote:
> > I mean, to my knowledge, there is no reason why a type should be
> > allocated on the heap (https://docs.python.org/2/c-api/typeobj.html
> > ) to
> > be able to change its attributes at Python level.
> One reason is sub-interpreter support: you can have multiple
> interpreters per process, and those shouldn't influence each other.
> (see https://docs.python.org/3/c-api/init.html#sub-interpreter-suppor
> t)
> With heap types, each sub-interpreter can have its own copy of the
> type
> object. But with builtins, changes done in one interpreter would be
> visible in all the others.

Yes, this could be a reason, but if you don't rely on such a feature
neither implicitly nor explicitly ?

I mean, our types are built-in and should be considered as immutable
across interpreters. And we (as most users I guess) are only running
one interpreter.

In case several intepreters are used, it would make sense to have a
non-heap type that would be seen as a singleton across all of them, no
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